The present invention relates to a motor and a blower.
Japanese Laid-Open Patent Publication No. 2007-181303 describes a prior art example of known motor including a stator having the so-called Lundell structure and a rotor with a permanent magnet opposing the stator in the radial direction and serving as a magnetic pole. The Lundell structure stator includes two stator cores each having an annular shape and including a plurality of claw poles arranged in a circumferential direction. The two stator cores are combined so that their claw poles are alternately arranged in the circumferential direction. A coil portion is arranged between the two stator cores in an axial direction. The coil portion cause the claw poles of the two stator cores to function as magnetic poles that differ alternately.
In the motor described in Japanese Laid-Open Patent Publication No. 2007-181303, when the rotor and the stator are increased in diameter to enlarge the area of the gap between the stator and the rotor and increase the output, dead space is produced in an inner circumferential portion. This is not desirable when reducing the motor in size. In this regard, there is room for improvement.
In the motor described in Japanese Laid-Open Patent Publication No. 2007-181303, when sets of the Lundell structure stator and the permanent magnets of the rotor are arranged in the radial direction of the motor to increase the output, the stators generate heat that causes the motor to be hot. This may adversely affect the motor performance.
A further known Lundell motor includes a Lundell rotor provided with two rotor cores, each including claw poles arranged in the circumferential direction, and permanent magnets arranged between the rotor cores. The permanent magnets function to cause the claw poles of the two rotor cores to function as magnetic poles that differ alternately. Japanese Laid-Open Patent Publication No. 2014-161198 describes a Lundell motor including a Lundell stator in addition to the Lundell rotor. The rotor and the stator both have the Lundell structure. Thus, the Lundell motor is also referred to as a multi-Lundell motor.
The multi-Lundell motor has a feature in that the number of poles can be changed by changing the number of claw poles. This allows the number of poles to be easily increased.
In the Lundell stator of Japanese Laid-Open Patent Publication No. 2014-161198, the two stator cores have a tendency to be displaced in the rotational direction. When the two stator cores are displaced in the rotational direction, the claw poles are moved away from one another in the rotational direction. This may disturb the magnetic flux.
Furthermore, in the Lundell rotor, the two rotor cores have a tendency to be displaced in the rotational direction. When the two rotor cores are displaced in the rotational direction, the claw poles are moved away from one another in the rotational direction. This may disturb the magnetic flux.
Disturbance of the magnetic flux in the motor may generate vibration and noise.
Japanese Laid-Open Patent Publication No. 11-332200 describes a brushless motor used as a drive source for a blower. In the brushless motor, a stator includes a stator core, which includes teeth that extend in the radial direction, and a coil, which is wound around each tooth. A rotor of the motor includes a yoke, which is fixed to and rotated integrally with a rotation shaft, and permanent magnets, which are fixed to the yoke and serve as magnetic poles of the rotor.
In the motor for the blower described above, the number of poles may be changed in the rotor and the stator. In this case, the number of permanent magnets and the like need to be changed in the rotor. Further, the number, winding, and the like of coils need to be changed in accordance with the changed number of teeth in the stator. Thus, it is difficult to change the number of poles.